The core library (lwt package) contains the Lwt module, which defines
cooperative threads with all the primitives to manipulate them. It
also provides several general purpose modules, which do not depend on
any external package.

Lwt is shipped with two syntax extensions. The first one, contained in
the lwt.syntax package, aims to make coding with Lwt easier, and
to make code more readable. The second, contained in the package lwt.syntax.log, is a camlp4 filter which decreases the performance
penalty when using logging by inlining level tests.